Air cart fan control

ABSTRACT

A pressure gradient or differential in a product distribution line for conveying granular particulate material, including at least one of seed or fertilizer, in an air flow to an agricultural field consistently decreases as air speed and velocity in the product distribution line decreases until a critical air speed is reached. Below the critical air speed, the particulate material may become susceptible to falling out of the air flow to potentially cause a blockage in the system. Accordingly, pressure sensors arranged in the product distribution line can be used to generate an air flow at an optimum velocity above the critical air speed yet below a maximum air speed associated with inefficient operation. The air flow can be adjusted to maintain the optimum velocity despite changes in at least one of a type of particulate material or a rate at which the particulate material is metered.

FIELD OF THE INVENTION

The present invention relates generally to systems for distributingparticulate material to agricultural fields, and more particularly, tosuch systems having pressure sensors in product distribution lines forconveying the particulate material in which pressure gradientscalculated from the pressure sensors are used to control an air sourceto maintain an air flow at a velocity below a maximum velocityproducible by the air source and above a minimum velocity causing aminimum pressure gradient.

BACKGROUND OF THE INVENTION

Generally, a tractor or work vehicle tows seeding or fertilizingimplements via a hitch assembly that connects to a rigid frame of aplanter, seeder or fertilizer applicator. These crop production systemstypically include one or more delivery lines that carry particulatematerial, such as seed or fertilizer. In certain systems, groundengaging tools are used to break the soil to deposit the particulatematerial carried by these delivery lines. After depositing theparticulate material, each ground engaging tool is typically followed bya packer wheel that packs the soil on top of the deposited material. Forother crop production systems, particulate material may simply be spreadonto the crops.

In certain configurations, an air cart is used to meter and deliver theparticulate material through the particulate delivery lines to the soil.As the particulate material moves through the delivery lines, theparticulate material can create blockages in one or more of the deliverylines. Such blockages can cause uneven delivery of product and reducecrop yields overall.

It is known for certain crop production systems to drive particulatematerial through the delivery lines using very high air speed to entrainthe material in order to ensure the possibility of a blockage isreduced. However, driving the particulate material at such high airspeeds can cause other problems in the system, such as: damage to theparticulate material due to impacting surfaces at forces that are toogreat; missing depositing targets for the particulate material due tothe material bouncing on the ground; and/or consumption of excess powerby continuously requiring fans to produce the high air speeds. What isneeded is an improved system for depositing particulate material thateliminates one or more of the foregoing disadvantages.

SUMMARY OF THE INVENTION

The present inventors have recognized that a pressure gradient ordifferential in a product distribution line for conveying granularparticulate material, such as seed or fertilizer, in an air flow to anagricultural field consistently decreases as air speed (velocity) in theproduct distribution line decreases until a critical air speed isreached. Below the critical air speed, the particulate material maybecome susceptible to falling out of the air flow to potentially cause ablockage in the system. Accordingly, pressure sensors arranged in theproduct distribution line can be used to generate an air flow at anoptimum operating velocity above the critical air speed yet below amaximum air speed associated with inefficient operation. In one aspect,the air flow can be adjusted to maintain an optimum operating velocitydespite changes in the type of particulate material and/or rate at whichthe particulate material is metered.

In one aspect, total pressure drop and local pressure drops in specificlocations can be monitored along the path of the hose. The monitoreddata can be interpreted for control of an air source. Also, the hoserouting can be physically manipulated to respond more quickly byincreasing the diameter of a section of the hose (up to 15% larger)before any bend or even a straight section. By measuring the localpressure drop from an upstream point to a point on the larger diameterregion the trend that appears can give an earlier indication thatproduct may start falling out of the airstream before it actuallyhappens. As seeding tool widths get larger and conveying lines getlonger it may become even more beneficial to monitor product flow statusin these lines. Longer lines may also require higher air velocity tomove product effectively. Standard practice is to do a “fountain test”to ensure a 12-24 inch fountain of product is exiting one of the hosesat an opener on the outer section to set the air flow. Users who do notdo this can instead simply set their fan at a significantly high rate sothat the system never becomes blocked. However, with the increasing useof variable product application rates across the tool (varying seedand/or fertilizer rates according to a prescription map) a user may bewasting air. The present invention provides a system for monitoring thestatus of the product flow in the airstream to match the fountain test,or potentially even lower, to avoid blockages by controlling the fanbased on the product rate. The system can utilizes at least one localpressure measurement region, preferably at a known “high” pressure droplocation, to act as an early warning monitor of the product flow statusbefore the critical air speed is reached. The system can also utilizepressure taps so the total pressure drop can be monitored. A slightincrease in hose diameter (on the order of 5-20%) over the designatedlocal pressure region can help give provide an early predictivecharacteristic.

As a result, the fan can safely operate at a lower air speed, becausethe flow monitoring of the local regions gives early warning well beforesettling of product happens in the line. With the fan running safely atlower speeds, power savings can be realized in the system. Also, saferconveying conditions for seeds (reducing or eliminating damage) andfertilizer (reducing damage in the conveying line) can be achieved.Lower exit velocities into furrow also yields a higher probability thatmore product will end up where desired and be less susceptible tobouncing out of the soil furrow.

In one aspect, pressure taps can be added to the conveying line at aspecified local region depending on hose routing configurations. Atleast one pressure tap can be provided at a beginning and end of atleast one line in the system. Also, a slight increase in diameter over asection of pipe in a local pressure region can provide furtherimprovements. A controller can execute to monitor pressure trends versusair speed (or fan speed).

Air pressure taps in a primary conveying line can be monitored forpressure drops along the entire length. Local pressure drops along theline can also be monitored. For representation here [3b] is straightsection before the bend where two pressure taps are located 0.5-2 mapart. The location of this local pressure measurement region is moreeffective if it is located at a region along the line that would be morelikely to plug or considered “high” pressure drop regions. For thisrepresentation just before the bend makes sense. These local pressureregions do not need to be before a bend, they could easily be on astraight section anywhere along the line but to minimize the number oflocal pressure regions it is wise to aim for a “high’ pressure dropregion along the distribution system. It is important to note thatmultiple local regions along the pipe could be monitored for even moreresolution. Monitoring these pressure drops along the lines in relationto fan speed (air flow or air velocity if that sensor is present), aconsistent decrease in pressure drop per unit length of hose line length(kPa/m) with a decrease in air velocity down (m/s) can be measured, downto a minimum. This minimum is considered the critical conveying velocityand is really the lowest conveying velocity you can achieve beforeproduct actively starts falling out of the airstream (see FIGS. 4 and 5for a visual representation).

In another aspect, a manual procedure of setting a fan speed bymonitoring product flow height can be replaced. Instead, an operator canset an operating point using measured values from one or moredifferential pressure sensors, particle speed sensors, or air speed/flowsensors. A table of predetermined set-point values that providesatisfactory product flow performance could be referenced by a controlsystem of the air cart/drill which could be determined at a factoryand/or by an operator. Environmental sensors, such as temperature(in-line and ambient), relative humidity, and/or barometric pressure,could be measured in conjunction with the previous sensing options.These environmental sensors could be incorporated into the controlsystem for establishing pre-determined set-point values and activelycontrolling the fan. For example, the same fan setting can result indifferent carrying capacities depending on ambient operating conditions.Regardless of operator-selected and/or factory-set operating points, thecontrol system could modify flow to a hydraulic motor that powers apneumatic conveying fan such that the difference between the set-pointand sensor value(s) is minimized, thereby keeping the pneumaticconveying system operating in a satisfactory performance state while theair drill/car control system is engaged.

In another aspect, a process can be implemented for automaticallylearning an optimum set-point for the control system of the pneumaticconveying system of an air cart/drill assembly, with minimal user input.A calibration procedure can be initiated which first determines if theselected product mass flow rate is new (i.e., the system has notoperated at this mass flow rate before, and thus a calibration valueneeds to be determined). If the current mass flow rate is not new, thena previously established safe air speed, v_(safe), can be recalled andcan be the set-point for the control system for operation. With a newproduct mass flow rate (i.e., v_(safe) for this product mass flow ratehas not been established), the target air speed can be set to a defaultmaximum value, v_(default), to ensure that plugging will not occur(since the air speed will be excessively high to begin with). Once themeasured air speed has achieved v_(default), a measured pressuregradient across a monitoring region can be recorded. The air speed canthen be decreased by a small increment by reducing the fan speed. Asshown and described more fully below, including at FIGS. 4 and 5, atthis newly established speed, another pressure gradient measurement canbe recorded. With two pressure gradient measurements at two differentspeeds, a slope of the pressure gradient vs. air speed curve can beapproximated by the most recent pressure gradient measurement subtractedfrom the prior pressure gradient measurement, divided by the most recentair speed setting subtracted from the prior air speed setting. If thesubtracted quantities are both positive, then the slope of the operatingcurve in the current region is positive, and the new operating point isto the right of v_(critical). The current air speed is saved as anintermediate value of v_(critical) because, until a lower air speed canbe tested, the current air speed is the last known value to the right ofthe true critical air speed. The process can be repeated by reducing thefan speed by an increment and measuring the pressure drop in the systemafter reaching the new steady-state air speed. If the difference inpressure gradient measurements has a sign opposite to the change in airspeed, the new operating point represents an increase in pressuregradient for a decrease in air speed. This new point is to the left ofthe true critical air speed, therefore the previous air speed setting isthe closest known value to the critical air speed. The previous airspeed remains as v_(critical). To maintain a safe operating margin fromair speeds that risk plugging, a margin δ can be added to v_(critical).Finally, v_(safe), the safe operating target air speed for the currentproduct mass flow can be calculated as v_(safe)=v_(critical)+δ. Thevalue of δ can be either pre-programmed during product development orset by the operator, for example. Aside from product type, andpotentially product mass flow rate (either of which may be provided froman operator to operate an air cart), δ could be the onlyoperator-determined input value to operate the system. This calibrationprocedure could be done manually or automatically via a controller orISO Bus Class 3 operation with minimal to no input from an operator.

In another aspect, changes in cross-sectional dimensions of a pneumaticconveying pipe/hose can be used to determine if deviations from acurrent state of a pneumatic conveying system will increase the risk ofplugging the system. By applying an effect in which changes incross-sectional diameter have on flow conditions, a control system canbe applied to a candidate region of the pneumatic conveying system. Aset-point determined from the automatic fan control calibrationprocedure above can then be used to inform the set-point for controllingthe fan. This may eliminate a need for the operator- orfactory-determined safe operating points to be pre-determined. Thus,after a system state diagram is created from a calibration method, anauto fan control method can simply follow a system state diagram toensure the system operates in an efficient range. This range can be aslow as the pressure minima or as high as the known fountain test setpoint as desired. In making the seeding system self-learning, utilizingthe auto calibration procedure with the flow monitoring procedure, thesystem can determine where the pressure minima is for each product andbe able to predict well in advance before arrival in the pressure minimaregion. Increasing product mass rate wili shift the curves up and to theright slightly, but this can be established with the auto calibrationprocedure so the fan control can follow the state diagram for safe andefficient conveying. This type of control system may be advantageouswhen used with fully or autonomous seeding systems.

Specifically then, one aspect of the present invention can provide asystem for distributing particulate material to an agricultural field,including: a meter module configured to dispense particulate material toa product distribution line; an air source configured to entrain theparticulate material in an air flow for transferring the particulatematerial through the product distribution line; first and secondpressure sensors arranged at first and second locations of the productdistribution line, respectively, the first pressure sensor beingarranged at a first location nearer to the meter module and the secondpressure sensor being arranged at a second location further from themeter module, in which each pressure sensor is configured to indicate apressure at a location in the product distribution line; and acontroller in communication with the air source and the first and secondpressure sensors. The controller can execute a program stored in anon-transient medium to: determine a pressure gradient in the productdistribution line by calculating a difference between first and secondpressures indicated by the first and second pressure sensors,respectively; and control the air source to maintain the air flow at avelocity below a maximum velocity producible by the air source and abovea minimum velocity causing a minimum pressure gradient.

Other aspects, objects, features, and advantages of the invention willbecome apparent to those skilled in the art from the following detaileddescription and accompanying drawings. It should be understood, however,that the detailed description and specific examples, while indicatingpreferred embodiments of the present invention, are given by way ofillustration and not of limitation. Many changes and modifications maybe made within the scope of the present invention without departing fromthe spirit thereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred exemplary embodiments of the invention are illustrated in theaccompanying drawings in which like reference numerals represent likeparts throughout.

FIG. 1 is a side view of an exemplar agricultural implement coupled toan air cart which includes a system for distributing particulatematerial to an agricultural field in accordance with an aspect of theinvention;

FIG. 2 is a top view of the agricultural implement coupled to the aircart of FIG. 1;

FIG. 3 is a schematic diagram of the system for distributing particulatematerial of FIG. 1;

FIG. 4 is a first graph illustrating an exemplary state diagram in whichchanges in pressure gradients with changes in air flow, including withcomparison to an upstream section of a product distribution line, in thesystem of FIG. 1;

FIG. 5 is a second graph illustrating an exemplary state diagram inwhich changes in pressure gradients with changes in air flow, includingwith comparison to a downstream section of a product distribution line,in the system of FIG. 1;

FIG. 6 is a process flow for calibration of an operating velocity forair flow in the system of FIG. 1; and

FIG. 7 is a graph illustrating exemplary predetermined air flow settingsfor distributing particulate material at differing flow rates inaccordance with an aspect of the invention.

These and other features and advantages of the invention will becomeapparent to those skilled in the art from the following detaileddescription and the accompanying drawings. It should be understood,however, that the detailed description and specific examples, whileindicating preferred embodiments of the present invention, are given byway of illustration and not of limitation. Many changes andmodifications may be made within the scope of the present inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and specifically to FIG. 1, a side view ofan exemplar agricultural implement 10, which may be a seeding implementor tool, coupled to an air cart 12 having a control system 14 isprovided in accordance with an aspect of the invention. The implement 10includes multiple row units 16 and multiple distribution headers 17supported by a frame 18. Each distribution header 17 is configured toreceive agricultural particulate material, such as seed or fertilizer,from the air cart 12, and to route the product to each row unit 16. Therow units 16, in turn, may be configured to deposit the agriculturalproduct onto the soil as the implement 10 travels across an agriculturalfield. As shown, the air cart 12 can be coupled to the implement 10 viathe frame 18. The air cart 12 may include one or more product storagetanks 22 configured to store one or more agricultural products(particulate material). Each product storage tank 22 is coupled to acorresponding metering subassembly 28, which includes multiple metermodules 24, each coupled to a corresponding primary product distributionline 26 (primary lines) that is configured to distribute agriculturalproduct to one or more corresponding headers 17 of the implement 10. Themeter modules 24 may be in fluid communication with the headers 17. Eachmeter module 24 may include an actuator and a meter roller, where theactuator may be configured to drive the meter roller to dispenseagricultural product from the storage tanks 22. In some embodiments, themeter module 24 may include a gate and the actuator may drive the gate.The meter modules 24 may be controlled by the control system 14. An airsource 27 which could comprise an electric or hydraulic fan provides anair flow to each of the primary lines 26. The metered agriculturalproduct is entrained within the air flow and pneumatically transferredto the one or more corresponding headers 17 of the implement 10. Whiletwo meter modules 24 and two primary lines 26 are shown for clarity, itshould be appreciated that, in certain embodiments each meteringsubassembly 28 may include at least 4, 6, 8, 10, 1.2, 14, 16, 18, 20 ormore meter modules 24 and/or primary lines 26. Furthermore, one metermodule 24 may provide the particulate material to one or more primarylines 26 which could be a subset of the primary lines 26. Additionally,while two headers 17 are shown for clarity, it should be appreciatedthat in some embodiments the implement 10 may include at least 1, 2, 4,6, 8, 10, 12 or more headers 17. It should also be appreciated thatwhile two row units 16 are shown for clarity, in certain embodiments,the implement 10 may include at least 4, 6, 8, 10, 12, 14, 16, 18, 20 ormore row units 16, and furthermore, that each primary line 26 mayprovide the particulate material to any suitable number of row units 16.Similarly, while one product storage tank 22 is illustrated by way ofexample, it should be appreciated that in certain embodiments the aircart 12 may include at least 2, 3, 4, 5, 6 or more product storage tanks22.

With additional reference to FIG. 2, a top view of the agriculturalimplement 10 coupled to the air cart 12 of FIG. 1 is provided. Asdepicted, the implement 10 includes six sections 30 attached to theframe 18 of the implement 10. Each section 30 includes multiple rowunits 16 attached to crossbars 32. Laterally displacing the row units 16in the illustrated manner may enable a dense disbursement of productacross a wide swath of soil. In addition, each section 30 may includeone header 17 that receives agricultural product metered by a respectivemeter module 24 into a respective attached primary line 26. As such,there may be six meter modules 24 and six primary lines 26 in thedepicted embodiment, one for each header 17, for example. The headers 17may route the product to the respective multiple row units 16 todistribute the product to the ground. In some embodiments, each section30 may include any number of suitable headers 17 and/or row units 16.The sections 30 may have any suitable configuration.

In accordance with an aspect of the invention, the system can includemultiple pressure sensors 40 arranged at predetermined locations of oneor more of the primary lines 26, such as a first pressure sensor 40 aarranged at first location of a primary line 26 a nearer or proximal tothe meter module 24 a, such as at a region of the air cart 12, and asecond pressure sensor 40 b arranged at second location of the sameprimary line 26 a further from or distal to the meter module 24 a, suchas at a region of the implement 10 near a crossbar 32. Each pressuresensor 40 can be configured to indicate a static or dynamic pressuremeasurement at a location in the primary line 26 where the pressuresensor is installed. The pressure sensor 40 can provide the pressurevalue to a controller for operation and control in the system asdescribed, herein. Each pressure sensor 40 could comprise, for example,a pressure tap consisting of hole in the primary line 26 with a pressuretransducer (a device which generates an electrical signal as a functionof the pressure imposed) mounted therein. Additional pressure sensors40, such as a third pressure sensor 40 c arranged at a third location ofthe primary line 26 a, between the first and second pressure sensors 40a and 40 b, respectively, can be included in the same primary line 26for even more detailed monitoring.

With additional reference to FIG. 3, a schematic diagram of a portion ofan embodiment of the implement 10 and the air cart 12 is provided. Tofacilitate discussion, one product storage tank 22 and its correspondingmetering subassembly 28 is shown. However, it should be understood thatthe air cart 12 may include any suitable number of storage tanks 22, andthe control system 14 may provide one metering subassembly 28 for eachstorage tank 22. As shown, the metering subassembly 28 includes twometer modules 24 (e.g., a first metering module and a second meteringmodule), although the metering subassembly 28 may include any suitablenumber of meter modules 24, as noted above. In the illustratedembodiment, each meter module 24 is configured to meter the particulatematerial into a corresponding primary line 26. Additionally, the airsource 27 is configured to entrain the particulate material in an airflow for transferring the particulate material through each primary line26 to a distribution header 17 of the implement 10. Although a singleair source 27 is shown for providing an air flow for multiple primarylines 26, in other aspects, multiple air sources 27 could be used forindividually providing the air flow to one or more primary lines 26. Theparticulate material entrained in the air flow, in turn, can betransferred the distribution header 17. The distribution header 17, inturn, can distribute the entrained particulate material into one or morecorresponding secondary lines 33 extending to a corresponding row unit16. Each meter module 24 and corresponding primary line 26 may thusprovide agricultural product to separate sections 30 (e.g., a firstsection and a second section) of the implement 10. Because each metermodule 24 may be separately controlled, the row units 16 of one section30 may apply the particulate material at a different rate than the rowunits 16 of another section 30. Thus, the particulate material may beapplied at different rates across a width of the implement 10, and theapplication rate provided by each section 30 may be adjustedindependently as the implement 10 travels across the field. As notedabove, it should be appreciated that although each meter module 24 isshown coupled to a single corresponding primary line 26, in someembodiments, each meter module 24 may be coupled to two or more primarylines 26, and thus may deliver product to two or more sections 30 (e.g.,a subset of sections 30), for example.

As shown, each meter module 24 includes an actuator 50 (e.g., motor)configured to actuate (e.g., drive rotation of) a respective meterroller 51 (e.g., meter). In some embodiments, each actuator 50 may driverotation of a drive shaft coupled to the respective meter roller 51.Although each meter module 24 includes the actuator 50, in someembodiments, the respective meter roller 51 of each meter module 24 maybe driven into rotation via any suitable mechanism. The control system14 also includes a controller 52 that may be located on the air cart 12and/or be communicatively coupled to each the pressure sensors 40, theair source 27 and/or the metering subassembly 28. The controller 52 isconfigured to receive feedback from the pressure sensors 40 and controlthe air source 27 to increase or decrease the air flow as desired. Inone aspect, the controller 52 can control the air source 27 to increaseor decrease the air flow, in response to a change in a pressure gradientmeasured between pressure sensors 40 in a primary line 26, such as byincreasing or decreasing power to an electrically driven fan and/orhydraulic fluid to a hydraulically driven fan. The controller 52 canalso be configured to control each actuator 50 to adjust a metering rate(e.g., meter roller turn rate) of its respective meter module 24. Incertain embodiments, the controller 52 is an electronic controllerhaving electrical circuitry configured to process signals (e.g., signalsindicative of a prescription rate map and/or prescribed applicationrates) from an input 54 (e.g., map or rate input, position, speed,product delay, width and/or geometry of respective geographic regions ofthe field) and/or from other components of the metering system 14. Forexample, the input 54 may be configured to provide signals indicative ofdesired product application rates for various regions of the field. Insome embodiments, the input 54 may be a Human Machine Interface (HMI)having a processor and a memory, and the input 54 may be used to receiveinput from an operator to determine target application types (e.g.,seed(s), such as peas or canola, and/or fertilizer(s)) and/or rates(e.g., in units of mass per area) and to provide the target applicationtypes and/or rates to the controller 52.

In the illustrated embodiment, the controller 52 includes a processor,such as the illustrated microprocessor 56, and a memory device 58. Thecontroller 52 may also include one or more storage devices and/or othersuitable components. The processor 56 may be used to execute software,such as software for controlling the air source 27 and/or the meteringsubassembly 28 in the control system 14. Moreover, the processor 56 mayinclude multiple microprocessors, one or more “general-purpose”microprocessors, one or more special-purpose microprocessors, and/or oneor more application specific integrated circuits (ASICS), or somecombination thereof. For example, the processor 56 may include one ormore reduced instruction set (RISC) or complex instruction set (CISC)processors.

The memory device 58 may include a volatile memory, such as randomaccess memory (RAM), and/or a nonvolatile memory, such as ROM. Thememory device 58 may store a variety of information and may be used forvarious purposes. For example, the memory device 58 may storeprocessor-executable instructions (e.g., firmware and/or software) forthe processor 56 to execute, such as instructions for controlling theair source 27 and/or the metering subassembly 28 in the control system14. The storage device(s) (e.g., nonvolatile storage) may includeread-only memory (ROM), flash memory, a hard drive, or any othersuitable optical, magnetic, or solid-state storage medium, or acombination thereof. The storage device(s) may store data (e.g., aprescription rate map, location data, implement speed data, or thelike), instructions (e.g., software or firmware for controlling the airsource 27, the metering subassembly 28 or the like) and/or any othersuitable data. The processor 56 and/or memory device 58, or anadditional processor and/or memory device, may be located in anysuitable portion of the system. For example, a memory device storinginstructions (e.g., software or firmware for controlling portions of thecontrol system 14, or the like) may be located on the air cart 12.

In addition, one or more air speed sensors 60 can be arranged in one ormore of the primary lines 26. Each air speed sensor 60 can be configuredto indicate an air speed measurement at a location in the primary line26 where the air speed sensor is installed. The air speed sensor 60 canprovide the velocity value to the controller 52 for operation andcontrol in the system, including for improved fan control, as describedherein. In one aspect, with feedback from the air speed sensor 60, thecontroller 52 can executes a closed loop control system to maintain theair flow at a desired velocity, such as by executingproportional-integral-derivative control with the desired velocity as aset point and the air speed sensor 60 providing feedback.

The present inventors have recognized that a pressure gradient ordifferential in the primary lines 26, when conveying the particulatematerial in an air flow, consistently decreases as velocity in theprimary lines 26 decreases until a “critical” air speed is reached.Below the critical air speed, the particulate material may becomesusceptible to settling out of the air flow to potentially cause ablockage in the system. By way of example, with additional reference toFIG. 4, a first graph 70 of pressure gradients in a primary lines 26 ona vertical axis (y-axis), versus velocity (or air speed) in the primarylines 26 on a horizontal axis (x-axis), for a given particulate materialat a given particulate mass flow rate, is provided. In a first curve 72,representing pressure gradient measurements across the entire primaryline 26 which may be determined by the controller 52, from the firstpressure sensor 40 a at one end of the primary line 26 to the secondpressure sensor 40 b at another end of the primary line 26, a consistentdecrease in pressure gradient with a decrease in velocity can beobserved in an operating region 74. For example, from a maximum velocity76 of air flow in a primary line 26 that is producible by the air source27, such as 20 m/s, to a critical air speed 78 that occurs when the airflow produced by the air source 27 is decreased, such as 13.5 m/s, thepressure gradient in the primary line 26 consistently decreases fromabout 90 Pa/m to about 50 Pa/m. This results in a positive slope of thefirst curve 72 (left-to-right). At the critical air speed 78, adifferential pressure minima 80 (minimum pressure gradient) occurs. Fromthe critical air speed 78, with further decreases of the air flowproduced by the air source 27, the pressure gradient in the primary line26 increases sporadically.

As a result, the controller 52, controlling the air source 27 andreceiving feedback from the pressure sensors 40, can produce an air flowand determine a pressure gradient for the air flow in the primary line26 (product distribution line) by calculating a difference between thefirst and second pressures indicated by the first and second pressuresensors 40 a and 40 b, respectively. The controller 52 can also adjustthe air speed by adjusting the air source 27 to locate the differentialpressure minima 80. The controller 52 can then adjust the air speed byagain adjusting the air source 27 to maintain the air speed at avelocity above a minimum velocity (above the critical air speed 78)causing the differential pressure minima 80, yet still below the amaximum velocity 76 producible by the air source 27. This can improveefficiency of the system in which damage to the particulate material dueto impacting surfaces at excessive speed may be reduced; missingdepositing targets for the particulate material due to the materialbouncing on the ground may be reduced; and/or consumption of excesspower by continuously requiring fans to produce higher air currents maybe avoided. In one aspect, the controller 52 can adjust the air speed byadjusting the air source 27 to maintain the air speed at an operatingvelocity 81 that is configured to be greater than the minimum velocity(above the critical air speed 78) by a predetermined margin, such as anadditional 1 m/s, while still achieving benefits with reduction in theair speed as described above.

In a second curve 82, representing pressure gradient measurements whichmay be determined by the controller 52 across an upstream section of theprimary line 26 that is nearer (proximal) to the air cart 12, such asfrom the first pressure sensor 40 a at one end of the primary line 26 tothe third pressure sensor 40 c (between the first and second pressuresensors 40 a and 40 b, respectively), a similar pattern to the firstcurve 72 is apparent. However, based on the location of the differentialmeasurement of the second curve 82, being at the upstream section nearerto the air cart 12, the differential pressure minima of the second curve82 occurs at a “settling” speed 84 in which the particulate material maysettle out of the air flow and begin rolling along the primary line 26.Pressure monitoring of the upstream section by the controller 52provides increased resolution as to events in the upstream section ofthe primary line 26. This can provide further insight for monitoringpressure differentials and configuring an air speed set point inpneumatic conveying systems with variable constructions andarrangements.

In addition, with further reference to FIG. 5 in which like referencenumerals represent like parts throughout, with the third pressure sensor40 c (between the first and second pressure sensors 40 a and 40 b,respectively), a second graph 90 illustrates a third curve 92 showingadditional pressure gradient measurements which may be determined by thecontroller 52 across a downstream section of the primary line 26 that isfurther from (distal to) the air cart 12, such as from the secondpressure sensor 40 b to the third pressure sensor 40 c (between thefirst and second pressure sensors 40 a and 40 b, respectively). Asimilar pattern to the first curve 72 is apparent. However, based on thelocation of the differential measurement of the third curve 92, being atthe downstream section further from the air cart 12, the differentialpressure minima of the third curve 92 occurs at an “early warning” speed86, such as 16.5 m/s, indicating a trend toward the critical andsettling air speed 78 and 84, respectively. In one aspect, the earlywarning speed 86 could be determined by the controller 52 as anoperating velocity for the air source 27 for safest operation, withheightened margin, such as an additional 3 m/s, while still achievingbenefits with reduction in the air speed as described above.

The controller 52 can increase or decrease a rate in which the metermodule 24 dispenses the particulate material. The controller 52 can alsochange a type of particulate material being dispensed, such as fromanother product storage tank 22. Either of these actions could be taken,for example, upon receiving an input from an operator, such as via theinput 54, and/or upon determining a new location on a prescription map,such as via a location sensor 53, which could comprise a GlobalPositioning System (GPS), comparing a result to a locally storedprescription map. Either a change in the rate of dispensing or a changein the type of particulate material being dispensed could cause a changein the pressure curves illustrated in the first and second graphs 70 and90, respectively, meaning a change in pressure gradients. Such changescould be monitored by the controller 52 for increasing or decreasing theair speed in response to a new operating velocity based on new pressureminima values as described above.

In one aspect, a diameter of the product distribution line can increasebetween the aforementioned upstream and downstream sections formonitoring with even greater sensitivity. By physically changing thediameter of the product distribution line, the pressure measurements ofFIGS. 4 and/or 5 can be determined by the controller 52 with evengreater speed for an early predictive characteristic. For example,referring again to FIG. 3, a diameter of the primary lines 26 can changebetween an upstream section 61, including the first pressure sensor 40a, and a downstream section 62, including the second pressure sensor 40b. The diameter of the primary lines 26 at the downstream section 62could be on the order of 5-20% larger than the diameter of the primarylines 26 at the upstream section 61. Moreover, the aforementioned changein diameter could be advantageously implemented before any bend (or evena straight section) of the primary lines 26. For example, referringagain to FIG. 2, the primary lines 26 include several straight sectionwith a first bend 94 of some angle, which could be less than or greaterthan 90°, at the implement 10, toward inner sections 36 of the frame 18,followed by a second bend 96, which could also be less than or greaterthan 90°, toward crossbars 32 of the frame 18, including toward theouter sections 34. The change in diameter could be implemented beforethe first bend 94, as contemplated in FIG. 3, and/or before the secondbend 96, including, for example, with successively increasing changes indiameter along the primary lines 26.

Referring now to FIG. 6, the controller 52 can execute a calibrationprocess flow 100 for automatically learning an optimum operatingvelocity for air speed in the system with minimal user input. Beginningat step 102, the controller 52 can begin the calibration proceduremanually when triggered by an operator, and/or automatically whentriggered by operation in the field, upon detecting a change in acurrent particulate material type being dispensed and/or a rate ofdispensing the particulate material (mass flow rate). Next, at decisionstep 104, the controller 52 can determine whether a current particulatematerial type being dispensed and/or a rate of dispensing theparticulate material (mass flow rate) is new to the system. If thecurrent particulate material type and/or rate is not new (“No”), then atstep 106 a previously established operating velocity for air speed inthe system can be retrieved from a data structure held in the memorydevice 58 for rapid configuration.

However, if the current particulate material type and/or rate is new(“Yes”), then a new operating velocity for the product mass flow ratecan be established beginning at step 108. To do so, the controller 52can control the air source 27 to produce the air speed at a defaultinitial velocity (v_(default)). The initial velocity is preferably amaximum velocity producible by the air source 27. This can ensure thatplugging or blockages do not occur in the system (since the air speedwill be excessively high to begin with). Then, at step 110, once themeasured air speed has achieved the initial velocity (v_(default)), ameasured pressure gradient across a monitoring region in one or more ofthe primary lines 26 can be recorded. Then, at step 112, the controller52 can control the air source 27 to lower the velocity of the air flowby an increment, such as by reducing the fan speed. Then, at step 114,at this newly established, incrementally lower speed, another pressuregradient measurement can be recorded.

Next, at decision step 116, with two pressure gradient measurements attwo different velocities or speeds having been recorded, a slope of thepressure gradient versus air speed curve can be approximated by the mostrecent pressure gradient measurement subtracted from the prior pressuregradient measurement, divided by the most recent air speed settingsubtracted from the prior air speed setting. This essentially constructsthe first and/or second graphs 70 and/or 90, respectively, as discussedabove with respect to FIGS. 4 and 5. If the subtracted quantities areboth positive, then the slope of the operating curve in the currentregion is positive, with the new operating point in the operating region74 (to the right of the minimum velocity (v_(critical))) (“Yes”). Then,at step 118, the current air speed can be saved as an intermediate valueof v_(critical) because until a lower air speed can be tested, thecurrent air speed is the last known value to the right of the truecritical air speed. Then, at step 120, the index can be incremented by1, and returning to step 112, a new (lower) air speed can be set,followed by the pressure gradients being measured again upon the systemreaching this new air speed at step 114. This loop of repeatedlydetermining a pressure gradient in one or more of the primary lines 26and controlling the air source 27 to lower the velocity of the air flowby an increment can continue until a minimum velocity for the air flowcausing a minimum pressure gradient is determined.

Eventually, at decision step 116, the slope of the operating curve inthe current region may be determined to be negative, with the newoperating point being outside of the operating region 74 (to left rightof v_(critical)) (“No”) for proceeding to step 122. This can occur whenthe difference in pressure gradient measurements has a sign opposite tothe change in air speed. The new operating point represents an increasein pressure gradient for a decrease in air speed resulting in a negativeslope. This new point is to the left of the true critical air speed,therefore the previous air speed setting is the closest known value tothe critical air speed. The previous air speed therefore remains asv_(critical). In one aspect, the minimum velocity (v_(critical)) couldbe configured by the controller 52, by adjusting the air source 27, asthe final operating velocity for the air flow in the system. This couldbe stored in the data structure, based on the particulate material typeand/or rate, establishing an operating velocity that can be retrieved ata later date at step 106.

However, preferably, at step 124, to maintain a safe operating marginfrom air speeds that risk plugging or blockage of the system, apredetermined margin δ can be added to v_(critical) for configuring theoperating velocity with margin (v_(safe)) for the air speed in thesystem. The v_(safe) operating target air speed for the current productmass flow can be calculated as v_(safe)=v_(critical)+δ. The value of δcan be either pre-programmed during product development or set by theoperator, for example. Aside from product type, and potentially productmass flow rate (either of which may be provided from an operator tooperate an air cart), δ could be the only operator-determined inputvalue to operate the system. The optimum operating velocity (v_(safe))could be configured by the controller 52, by adjusting the air source27, as the final operating velocity for the air flow in the system. Thiscould be stored in the data structure, based on the particulate materialtype and/or rate, establishing an optimum operating velocity that can beretrieved at a later date at step 106. The calibration procedure of FIG.6 could be done manually or automatically via a controller or ISO BusClass 3 operation, such as ISO 11783 communication and control, withminimal to no input from an operator.

In addition, the system could include one or more environmental sensors160 for measuring various environmental conditions for furthercompensating the operating velocity. The environmental sensors 160 couldinclude, for example, one or more temperature sensors 160 a inside theprimary line 26; an ambient temperature sensor 160 b external to the aircart 12; an ambient pressure sensor 160 c external to the air cart 12,and/or a humidity sensor 160 d external to the air cart 12. Thecontroller 52 could receive feedback from the environmental sensors 160and compensate the operating velocity corresponding to the air speedaccording to the environmental condition, such as increasing thevelocity of the air flow by 0.5 m/s when experiencing hot, humidenvironmental conditions, and/or decreasing the velocity of the air flowby 0.5 m/s when experiencing cold, dry environmental conditions.

For improved control, multiple predetermined air speed settings fordistributing differing particulate materials at differing flow ratesthrough pneumatic conveying systems of the system can be stored inaccordance with an aspect of the invention. Referring now to FIG. 7, agraph 150 illustrating a set of exemplary predetermined air speedsettings 152 for distributing a given type of particulate material atdiffering flow rates is provided in accordance with an aspect of theinvention. Like the graphs of FIGS. 4 and 5, the graph 150 can relatepressure gradients in primary lines 26 on a vertical axis (y-axis) tovelocities (or air speeds) in the primary lines 26 on a horizontal axis(x-axis). The set of exemplary predetermined air speed settings 152could be specific to a given particular granular particulate material,such as peas. This set could be stored with other sets for otherparticulate materials, such as sets for other types of seeds and/orfertilizers, in a data structure held in the memory device 58.Alternatively, a set of predetermined air speed settings could bespecific to a dispensing rate for different particulate materials.

In the graph 150, each predetermined air speed setting 152 couldcomprise a velocity for an air flow corresponding to the given type ofparticulate material and a given rate for dispensing particulatematerial. For example, the first predetermined air speed setting 152 acould comprise an optimum operating velocity which could be configuredfor an air flow corresponding to a first type of particulate material,such as peas, at a first rate for dispensing the first type ofparticulate material (a first mass flow rate “(m_(p))a”); the secondpredetermined air speed setting 152 b could comprise an optimumoperating velocity which could be configured for an air flowcorresponding to the same first type of particulate material (e.g.,peas) at a second rate for dispensing the first type of particulatematerial (a second mass flow rate “(m_(p))b”); and the thirdpredetermined air speed setting 152 c could comprise an optimumoperating velocity which could be configured for an air flowcorresponding to the same first type of particulate material (e.g.,peas) at a third rate for dispensing the first type of particulatematerial (a third mass flow rate “(m_(p))c”); and so forth. As shown,the dispensing rate associated with the first predetermined air speedsetting 152 a is greater than the dispensing rates associated with thesecond and third predetermined air speed settings 152 b and 152 c,respectively; and the dispensing rate associated with the secondpredetermined air speed setting 152 b is greater than the dispensingrate associated with the third predetermined air speed setting 152 c.These dispensing rates are further compared to an air only curve 161,without dispensing of any particulate material, by way of reference,which results in a consistent, relatively low pressure drop with slightincreases with increases in air speed.

Accordingly, a differential pressure minima for each predetermined airspeed setting, which occurs at increasing air speeds with increasingmass flow rates as provided by the differential pressure minima curve153, can be quickly referenced for minimum velocities (v_(critical)).With a predetermined margin δ added to each minimum velocity(v_(critical)), an optimum operating velocity (v_(safe)) 154 could bereadily retrieved by the controller 52 from the data structure forconfiguring the air speed according to the type of particulate materialand/or rate of dispensing. Moreover, this operating velocity (v_(safe))154 is quickly determined as an operating velocity that is less than adefault high velocity 162 which may be generic to all types and rates,which default could be a maximum velocity producible by the air source27 and/or a velocity determined from a “fountain” test, therebyresulting in immediate efficiencies. For example, when commanded todispense the first type of particulate material (e.g., peas) at amaximum dispensing rate, such as according to input from an operator ora location on a prescription map, the controller 52 could reference thefirst predetermined air speed setting 152 a to retrieve the operatingvelocity 154 a for rapid configuration of an optimum setting for an airflow generated by the air source 27. Such rapid retrieval andconfiguration may be particularly advantageously with fully autonomousseeding systems.

Although the best mode contemplated by the inventors of carrying out thepresent invention is disclosed above, practice of the above invention isnot limited thereto. It will be manifest that various additions,modifications and rearrangements of the features of the presentinvention may be made without deviating from the spirit and the scope ofthe underlying inventive concept.

What is claimed is:
 1. A system for distributing particulate material toan agricultural field, comprising: a meter module configured to dispenseparticulate material to a product distribution line; an air sourceconfigured to entrain the particulate material in an air flow fortransferring the particulate material through the product distributionline; first and second pressure sensors arranged at first and secondlocations of the product distribution line, respectively, the firstpressure sensor being arranged at a first location proximal to the metermodule and the second pressure sensor being arranged at a secondlocation distal to the meter module, wherein each pressure sensor isconfigured to indicate a pressure at a location in the productdistribution line; and a controller in communication with the air sourceand the first and second pressure sensors, the controller executing aprogram stored in a non-transient medium to: control the air source tomaintain the air flow at an initial velocity, wherein the initialvelocity is a maximum velocity producible by the air source; repeatedlydetermine a pressure gradient in the product distribution line bycalculating a difference between first and second pressures indicated bythe first and second pressure sensors, respectively; and control the airsource to lower the velocity of the airflow from the initial velocity,until a minimum velocity for the air flow causing a minimum pressuregradient sufficient to maintain entrained particulate material isdetermined; and control the air flow at a velocity greater than theminimum velocity by a predetermined margin, wherein a rate in which themeter module dispenses the particulate material increases or decreases,and wherein the controller executes to increase or decrease the air flowto maintain the velocity at the predetermined margin or calculates a newmargin.
 2. The system of claim 1, wherein a type of the particulatematerial in which the meter module dispenses changes, and wherein thecontroller executes to increase or decrease the air flow to maintain thevelocity at the predetermined margin or calculates a new margin.
 3. Thesystem of claim 2, wherein the particulate material is selected from thegroup consisting of seed and fertilizer.
 4. The system of claim 1,wherein the air source comprises a fan, and wherein the controllerexecutes to control the air source to increase or decrease the air flowby increasing or decreasing hydraulic fluid to the fan.
 5. The system ofclaim 1, further comprising an air speed sensor in communication withthe controller, wherein the air speed sensor is configured to indicate avelocity of the air flow in the product distribution line.
 6. A methodfor distributing particulate material to an agricultural field,comprising: dispensing particulate material from a meter module to aproduct distribution line; entraining the particulate material in an airflow produced by an air source for transferring the particulate materialthrough the product distribution line; determining a pressure gradientin the product distribution line by calculating a difference betweenfirst and second pressures indicated by first and second pressuresensors, respectively, wherein the first and second pressure sensors arearranged at first and second locations of the product distribution line,respectively, with the first pressure sensor being arranged at a firstlocation proximal to the meter module and the second pressure sensorbeing arranged at a second location distal to the meter module;controlling the air source to produce the air flow at an initialvelocity, wherein the initial velocity is a maximum velocity producibleby the air source; controlling the air source to lower the velocity ofthe air flow from the initial velocity, until a minimum velocity for theair flow causing a minimum pressure gradient sufficient to maintainentrained particulate material is determined; configuring the velocityfor the air flow to be greater than the minimum by a predeterminemargin, increasing or decreasing a rate in which the meter moduledispenses the particulate material, and increasing or decreasing the airflow to maintain the velocity above the predetermined margin orcalculating a new margin.
 7. The method of claim 6, further comprisingchanging a type of the particulate material in which the meter moduledispenses, and further comprising increasing or decreasing the air flowto maintain the velocity at the predetermined margin or calculating thenew margin.
 8. A system for distributing particulate material to anagricultural field, comprising: an air cart comprising: a productstorage tank configured to store particulate material; a meter moduleconfigured to dispense the particulate material from the product storagetank to a primary product distribution line; and a fan configured toentrain the particulate material in an air flow for transferring theparticulate material through the primary product distribution line; anagricultural implement comprising: a product distribution headerconfigured to receive the particulate material from the air cart throughthe primary product distribution line; and a plurality of row units,each row unit being configured to receive the particulate material fromthe product distribution header through a secondary product distributionline and deposit the particulate material to the agricultural field;first and second pressure sensors arranged at first and second locationsof the product distribution line, respectively, the first pressuresensor being arranged at a first location proximal to the meter moduleand the second pressure sensor being arranged at a second locationdistal to the meter module, wherein each pressure sensor is configuredto indicate a pressure at a location in the product distribution line;and a controller in communication with the fan and the first and secondpressure sensors, the controller executing a program stored in anon-transient medium to: control the fan to produce the air flow at aninitial velocity, wherein the initial velocity is a maximum velocityproducible by the air source; determine a pressure gradient in theproduct distribution line by calculating a difference between first andsecond pressures indicated by the first and second pressure sensors,respectively; and control the air source to lower the velocity of theair flow from the initial velocity until a minimum velocity and aminimum pressure gradient sufficient to maintain entrained particulatematerial is determined; and configure the velocity of the air flow to begreater than the minimum velocity by a predetermined margin, wherein arate in which the meter module dispenses the particulate materialincrease or decreases, and wherein the controller executes to increaseor decrease the air flow to maintain the velocity at the predeterminedmargin or calculates a new margin.
 9. The system of claim 8, wherein atype of the particulate material in which the meter module dispenseschanges, and wherein the controller executes to increase or decrease theair flow to maintain the velocity at the predetermined margin or the newmargin.
 10. The system of claim 8, wherein the particulate material isselected from the group consisting of seed and fertilizer.
 11. Thesystem of claim 8, wherein a diameter of the product distribution linechanges between the first and second locations.